This ingenious loop turns a simple artifact into a self-sustaining engine by letting Citanul Hierophants give your creatures the ability to tap for green mana, which fuels the casting cost of Sensei's Divining Top right back out of your library. Meanwhile, Crystal Skull, Isu Spyglass not only provides blue mana when needed but crucially grants you permission to cast historic spells—like the Top itself—directly from the top of your library without ever needing it in your hand. Traxos, Scourge of Kroog holds the physical labor of the loop together, standing ready to untap itself via its own triggered ability every single time you cast that historic artifact.